JP3161613B2 - Method of stabilizing aqueous emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for stabilizing an aqueous emulsion containing an acetoacetylated polyvinyl alcohol resin (hereinafter abbreviated as AA-PVA).

[0002]

2. Description of the Related Art Emulsions such as emulsion latexes and polyacrylate emulsions composed of natural rubber, polyisoprene, polybutadiene, chloroprene, polystyrene-butadiene, polymethylmethacrylate-butadiene, etc. are bonded. Agent,
It has a wide range of applications such as paints, fibers, textile processing, paper and leather processing, binders for various materials, and admixtures for cement and mortar. Depending on the purpose and application of such emulsions, those with moderate viscosity and structural viscosity exhibit excellent effects on workability, machine suitability, finished state, adhesiveness, etc., so that the inherent performance of the emulsion is impaired at all. AA as a means to easily satisfy the above required properties without
A method has been widely used in which a monomer is emulsion-polymerized by using an activated PVA as an emulsifier, or an AA-PVA is added as a protective colloid or a viscosity modifier to an emulsion.

[0003]

However, general emulsions contain aldehyde compounds, amine compounds, metal salts and the like as by-products during the polymerization reaction or as stabilizers, fungicides and the like. Easily causes a cross-linking reaction with an acetoacetyl group (hereinafter abbreviated as AA group). Therefore, when the AA-PVA is used in the emulsion for the above purpose, gelation occurs in a short period of time or the viscosity increases with time. Therefore, meticulous care is required for long-term storage of the emulsion, which is extremely inconvenient in actual use. As such a solution, for example, JP-B-60-36218 discloses that an AA-PVA-containing vinyl acetate emulsion contains one or more selected from sulfites, bisulfites, metabisulfites, and thiosulfates. There is a statement that the viscosity of the emulsion is stabilized by causing the emulsion. However, in such a method, although the increase in viscosity over time can be reduced, when the emulsion is used for an application such as an adhesive or a binder, the disadvantage that the water-resistant adhesive strength to a substrate is greatly reduced, and the emulsion has a disadvantage. There is a new problem that the use is very limited.

The inventors of the present invention have conducted various studies in order to solve the above-mentioned drawbacks. As a result, by adding an oxycarboxylic acid to a polyvinyl alcohol-based aqueous emulsion containing an isocyanate compound or an isocyanate polymer, the pot of the emulsion was prepared. Based on the finding that the life is prolonged (Japanese Patent Publication No. 56-15418), oxycarboxylic acid was added to an emulsion containing AA-PVA. However, in such a method, no satisfactory results were obtained in any of the adhesiveness of the emulsion and the viscosity stability, and it was difficult to adapt to the intended emulsion.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to obtain an emulsion having a sufficient viscosity and a stable viscosity and hardly causing gelation. It has been found that such a purpose can be achieved when (A) oxycarboxylic acid and (B) one or more selected from sulfites, bisulfites, metabisulfites, and thiosulfates are contained. The invention has been completed. In the present invention, (A)
When both (A) and (B) are blended into an AA-PVA-containing emulsion, they exhibit an excellent effect of further improving the viscosity stability of the emulsion while having a sufficient adhesive force for the first time, Even if A) or (B) is used alone, it is impossible to obtain the desired emulsion, which is very disadvantageous in practical use. Hereinafter, the present invention will be described in detail.

[0006] The method for producing AA-PVA in the present invention is not particularly limited, and may be produced by any method, but is preferably obtained by reacting PVA with diketene. For example, a method in which PVA is dispersed in an acetic acid solvent and diketene is added thereto, or a method in which PVA is dissolved in a solvent such as dimethylformamide or dioxane in advance and diketene is added thereto. Also P
A method of obtaining AA-PVA by directly contacting VA with diketene gas or liquid diketene can also be employed. The PVA used for obtaining the AA-PVA is not particularly limited, but the residual acetic acid groups are 0.1 to 15 mol% and the average degree of polymerization is 300 to 260.
0, the average saponification degree is preferably in the range of 85 to 99 mol%.

The degree of AA conversion of AA-PVA is 0.05 to 20.
Mol%, more preferably in the range of 0.05 to 15 mol%. AA-P having an AA conversion degree of less than 0.05 mol%
In VA, the contribution of the emulsion to water resistance is small, which is not preferable. On the other hand, AA-PVA having an AA conversion degree of more than 20 mol% is not preferable.
In, the dispersion system is destroyed and a homogeneous emulsion state cannot be obtained, or the obtained emulsion has various inferior stability,
It is not preferable as a practical product.

[0008] The preparation of the emulsion containing AA-PVA in the present invention is not particularly limited.
AA-PVA is added to a synthetic resin emulsion obtained by an arbitrary method, in which a monomer is emulsion-polymerized using AA-PVA as an emulsifier or protective colloid, and a solution or melt of a synthetic resin is post-emulsified in the presence of AA-PVA. Are added to produce a more stable emulsion. Hereinafter, each case will be specifically described.

Method by Emulsion Polymerization This method is usually suitably carried out when producing a polymer emulsion of a vinyl compound. At the time of emulsion polymerization, a vinyl compound is added temporarily or continuously in the presence of water, AA-PVA and a polymerization catalyst, and is heated to 0.1 to 30 to 30% of the solid content of an ordinary emulsion polymer. % By weight, preferably about 2 to 20% by weight. If it is less than 2% by weight, a sufficient effect cannot be obtained, and if it is more than 20% by weight, the effect does not increase in proportion to the amount used. The AA-PVA
Can be added at the start of, during, or after the completion of emulsion polymerization, but is usually added at the start of, or during, the polymerization.

The vinyl compounds used in the present method include vinyl acetate, vinyl propionate, acrylates, methacrylates, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, styrene, ethylene, propylene, glycidyl acrylate, glycidyl. Glycidyl group-containing compounds such as methacrylate, glycidyl divinyl ether and glycidyl vinyl ether; methylol group-containing compounds such as N-methylol acrylamide and N-methylol methacrylamide; and alkoxy group-containing derivatives thereof, carboxylic amides such as acrylamide and methacrylamide, acrylic Acid, carboxylic acid such as methacrylic acid, divinyl adipate, divinyl succinate, triallyl cyanurate, diallyl fumarate, tria Rushitoreto, diallyl maleate, containing vinyl versatate and acetoacetyl group
Monomers, such as allyl having an acetoacetyl group,
Vinyl, (meth) acrylate compounds and the like,
These are homopolymerization or copolymerization. In particular, vinyl acetate alone or a copolymer mainly composed of vinyl acetate is preferred.

As the emulsion polymerization catalyst, a catalyst used in ordinary emulsion polymerization is used. Specific examples include aqueous hydrogen peroxide, ammonium persulfate, potassium persulfate alone or sodium metabisulfite, sodium bisulfite,
Combinations with dimethylaniline, tartaric acid, ascorbic acid .

Further, a nonionic surfactant and an ionic surfactant can be used in combination with the AA-PVA. Still other emulsifiers, for example, PVA, cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, etc.), polyacrylic acid derivatives, (anhydrous) maleic acid-
A vinyl ether copolymer, a (maleic anhydride) maleic acid-vinyl acetate copolymer, a vinyl acetate- (meth) allyl sulfonic acid (salt) copolymer saponified product, and the like can also be used in combination. In addition, various additives, preparation agents, and the like used in ordinary emulsion polymerization can also be appropriately used.

Method by post-emulsification This method is suitably carried out when preparing a synthetic resin emulsion which cannot be easily produced by emulsion polymerization. In this method, AA-PVA is dissolved in water, and a resin in the form of a solution is added dropwise thereto and stirred, or AA-PVA is added to the molten resin.
The aqueous solution of A may be dropped and stirred. There is no particular need for heating for emulsification, but if necessary,
What is necessary is just to heat to about 85 degreeC. There is no particular limitation on the substance to be emulsified, urethane resin, urea-formalin initial condensate,
Examples include phenol-formaldehyde initial condensate, alkyd resin, polyester resin, ketene dimer, silicone resin, wax, polypropylene, polyethylene and the like.

[0014] The amount of the AA-PVA somewhat varies depending resin content, etc. of the emulsion is required, but usually milk
0.1 to 30 wt% for the reduction target, preferably 1 to
It is selected from a range of about 25% by weight. If necessary, a polyoxyethylene-alkyl ether type together with the resin,
A nonionic activator such as a polyoxyethylene-alkylphenol type or a polyhydric alcohol ester type, or a cationic activator such as a higher alkylamine salt may be appropriately used in combination. These activators can also be mixed in the emulsified object.

This method is carried out by adding AA-PVA to the emulsion obtained by an arbitrary method to further improve the stability or increase the viscosity. Emulsions include natural rubber latex, styrene / butadiene emulsions,
Styrene / acrylic emulsion, cis-1,4 polyisoprene emulsion, chloroprene emulsion,
Acrylonitrile / butadiene emulsion, vinylpyridine emulsion, methyl methacrylate / butadiene emulsion, polyurethane emulsion, acrylic ester emulsion, vinyl acetate emulsion,
Examples include an ethylene / vinyl acetate emulsion, a vinyl chloride emulsion, a polystyrene emulsion, a polyethylene emulsion, a silicone emulsion, a polybutene emulsion, and a thiochol emulsion.

When adding AA-PVA to the emulsion, when adding the PVA as an aqueous solution, the aqueous solution is added to the emulsion while stirring it at room temperature. When adding the PVA powder, it is preferable to add the powder while stirring the emulsion and heat the mixture to 50 to 85 ° C., since uniform mixing is completed in a short time. or,
It is of course possible to mix the emulsion containing AA-PVA obtained in the above with the emulsion obtained by any method. The amount of the AA-PVA used is about 1 to 40% by weight, preferably 2 to 30% by weight, based on the solid content of the emulsion.

The AA-PVA-containing aqueous emulsion thus obtained is adjusted as it is or as appropriate. Since the solid content of the emulsion used in the present invention varies depending on its use, it cannot be specified unconditionally, but it is usually from 30 to 30%.
A range of 60% by weight is suitable.

The AA-PVA-containing emulsion obtained as described above contains (A) oxycarboxylic acid and (B) one selected from sulfites, bisulfites, metabisulfites and thiosulfates.
The seed or two or more drugs are blended. Examples of (A) include oxymonocarboxylic acids such as lactic acid, glycolic acid, oxybutyric acid and ricinoleic acid, oxydicarboxylic acids such as malic acid and tartaric acid, oxytricarboxylic acids such as citric acid, and gallic acid, which are aliphatic oxycarboxylic acids. And aromatic oxycarboxylic acids such as salicylic acid. These can be used alone or in combination of two or more. (B) is one or more selected from sodium, potassium, ammonium and amine salts of sulfurous acid, bisulfite, metabisulfite and thiosulfate.

The amount of (A) is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the solid content of the aqueous emulsion containing AA-PVA.
The compounding amount of (B) is 0.01 to 5 parts by weight, preferably 0.02 to 2 parts by weight, based on 100 parts by weight of the solid content of the AA-PVA-containing aqueous emulsion. The weight mixing ratio of (A) and (B) is such that (A) / (B) is 1/10 to 10/1, preferably 1
/ 5 to 5/1 is appropriate.

As a method of blending (A) and (B), A
(A) and (B) may be added as a powder or an aqueous solution to the A-PVA-containing aqueous emulsion, and the mixture may be stirred and uniformly mixed.Preferably, before the AA-PVA and the emulsion are mixed, a predetermined amount of (A) and (A) are mixed. Premixing (B) with one or both of the AA-PVA and the emulsion has a remarkable effect of improving the stability of viscosity, and particularly, (A) and (B)
Is added to the emulsion side in advance, and an extremely good aqueous emulsion can be obtained. The pH of such an AA-PVA-containing aqueous emulsion must be adjusted to 3 to 9, preferably 4 to 7.5. If the pH is less than 3 or more than 9, long-term storage stability cannot be obtained.

The aqueous emulsion thus obtained has excellent adhesive strength, has no danger of thickening or gelling even when left for a long period of time, and is extremely excellent in storage stability. Depending on the further plasticizer,
Film forming aids such as high-boiling solvents, clay, calcium carbonate, kaolin, diatomaceous earth and other pigments, colored pigments such as titanium oxide, preservatives, insect repellents, rust inhibitors, defoamers, flour and wood flour, etc. A bulking agent can be appropriately blended and used.

The aqueous emulsion obtained in the present invention is suitable for an adhesive, a coating agent, a fiber processing agent, a paint, a cement admixture, a material for molding, and the like. In particular, the aqueous emulsion of the present invention has excellent adhesive strength. It is effective for applications such as adhesives and binders for paper, wood, plastics and fibers, as well as water-resistant cardboard and plywood. When such an aqueous emulsion is used as an adhesive, various crosslinking agents can be used in combination.

Examples of the crosslinking agent include monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde and glyoxylic acid, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maledialdehyde, and the like.
Dialdehydes such as phthalaldehyde, polyaldehydes such as starch, diamines such as hexamethylenetetramine, ethylenediamine, trimethylenediamine, phenylenediamine, polyamideamine resin, polyethyleneimine, dihydrazide compound, tolylenediisocyanate,
Amino-formaldehyde resins such as trimethylolpropane, triphenylmethane triisocyanate, isocyanate compounds such as xylene diisocyanate, alkylated methylol urea, alkylated methylol melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde, and further zirconium and zinc And polyvalent metal salts of alkali metals or alkaline earth metals such as magnesium, calcium, and aluminum, and oxides thereof.

[0024]

In the present invention, an aqueous emulsion containing AA-PVA is added to an aqueous emulsion containing (A) oxycarboxylic acid and (B) one selected from sulfites, bisulfites, metabisulfites, and thiosulfates. Alternatively, by containing two or more types, the emulsion viscosity is further stabilized while having sufficient adhesive strength, and the viscosity increase with time can be reduced, so that the emulsion can be stored for a long period of time without limiting the intended use. Can be.

[0025]

The present invention will be described below in more detail by way of examples.
In the examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 Styrene-butadiene-based latex (# DL-612,
Resin content 48%, viscosity 40 cps, manufactured by Asahi Kasei Kogyo Co., Ltd.)
To 38 parts, 30 parts of a 70% aqueous dispersion of talc (#SW, manufactured by Nippon Talc Corporation) was mixed. This is tartaric acid 1.0
And an aqueous solution containing 0.5 parts (in terms of solids) and 0.5 part (in terms of solids) of sodium bisulfite were added and mixed uniformly. 20 parts of AA-PVA (degree of polymerization 1500, degree of saponification 88 mol%, degree of acetoacetylation 5.7 mol%) are added to the mixture.
% Aqueous solution, and the whole is mixed uniformly to obtain a solid content of 4%.
A 3% aqueous emulsion was obtained. The standing stability and adhesive strength of the obtained aqueous emulsion were measured. The results are summarized in Table 2.

<Stability during Storage> (a) The viscosity immediately after mixing was measured at 25 ° C. using a B-type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.). (B) A part of the container was sealed and immersed in a constant temperature water bath at 60 ± 1 ° C. for 7 days, and the viscosity after 7 days was measured in the same manner as in (a). (C) A part of the mixture was sealed and left for 3 months in a room, and the viscosity was measured in the same manner as in (a).

[0027] <adhesive strength> aqueous emulsion 100 parts of polyisocyanate (Milionate MR, Nippon Polyurethane Co., Ltd.) 1
5 parts of the mixed adhesive was applied to both adhesive surfaces of two pieces of birch wood (manufactured by Japan Standard Test Panel Co., Ltd.) of 25 × 50 × 10 mm so as to have an application amount of 240 g / m ² (solid content), The two surfaces were brought into contact, compressed at 10 kgf / cm ² for 3 hours, decompressed, and left at room temperature for one week or more.

(Water-resistant water) After curing as described above, test pieces were
After being immersed in warm water of 3 ° C. for 3 hours, it was immersed in water of 20 ° C. until cooled, and measured in a wet state according to the compressive shear strength of JIS K6806 “aqueous polymer-isocyanate-based wood adhesive”.

(Repeating boiling) After curing, the test piece was immersed in boiling water for 4 hours, dried at 60 ± 3 ° C for 20 hours, immersed again in boiling water for 4 hours, and cooled in water at 20 ° C. And measured in compliance with the compressive shear strength of JIS K6806 "Aqueous polymer-isocyanate-based wood adhesive" in a wet state.

Comparative Example 1 An experiment was carried out in the same manner as in Example 1 except that tartaric acid and sodium bisulfite were not added.
Immediately after mixing the aqueous solution A, gelation started, and a coarse aqueous emulsion containing many coarse particles could not be obtained. Comparative Example 2 An experiment was carried out in the same manner as in Example 1 except that sodium bisulfite was not mixed. Table 2 summarizes the results. Comparative Example 3 An experiment was carried out in the same manner as in Example 1 except that tartaric acid was not mixed. Table 2 summarizes the results.

Examples 2 to 4 In Example 1, the chemicals shown in Table 1 were added, and an experiment was carried out according to the same example. Table 2 summarizes the results.

[0032]

[Table 1]

Example 5 Ethylene-vinyl acetate copolymer emulsion (ethylene: vinyl acetate = 22: 78 (weight ratio), resin content 50%,
0.5 part of tartaric acid (solid content) and 0.5 part of potassium metabisulfite (solid content) in 50 parts of viscosity 4500 cps)
Is added and mixed uniformly. Next, AA-PVA (polymerization degree 1400, saponification degree 9) was added to the mixture.
20% of 6 mol%, degree of acetoacetylation 6.1 mol%)
When 40 parts of an aqueous solution and 10 parts of calcium carbonate were added, a homogeneous aqueous emulsion having a solid content of 45% was obtained. The standing stability and adhesive strength of the obtained aqueous emulsion were measured according to Example 1. However, glyoxal (active ingredient 40%, Nippon Synthetic Chemical Industry) was used as a curing agent instead of polyisocyanate in the measurement of adhesive strength.
Was used. Table 2 summarizes the results.

Example 6 AA-PVA (Polymerization degree 1200, saponification degree 96 mol%,
A vinyl acetate resin emulsion emulsion-polymerized using 5 parts of an acetoacetylation degree (5.7 mol%) as an emulsifier (resin content 4
An aqueous solution containing 0.2 part of tartaric acid (in terms of solids) and 0.4 part of sodium bisulfite (in terms of solids) was added to 100 parts of the mixture, and the mixture was uniformly mixed.
An aqueous emulsion of was obtained. The standing stability and adhesive strength of the obtained aqueous emulsion were measured according to Example 1. Table 2 summarizes the results.

Comparative Example 4 An experiment was carried out in the same manner as in Example 6 except that sodium bisulfite was not mixed. Table 2 summarizes the results. Comparative Example 5 An experiment was carried out in the same manner as in Example 6 except that sodium bisulfite was not mixed. Table 2 summarizes the results.

Example 7 Citric acid 0.2 parts (in terms of solid content) in 55 parts of a styrene-acrylic copolymer emulsion (Polytron T-810, resin content 52%, viscosity 2200 cps, manufactured by Asahi Kasei Kogyo KK) And an aqueous solution containing 0.5 part (in terms of solid content) of sodium bisulfite was added and uniformly mixed.

Next, AA-PVA (degree of polymerization 1300, degree of saponification 96 mol%, degree of acetoacetylation 4.5 mol%) 1
45 parts of a vinyl acetate resin emulsion (resin content 45%, viscosity 15000 cps) obtained by emulsion polymerization using 0 part as an emulsifier were mixed with stirring to obtain an aqueous emulsion having a solid content of 48%. The standing stability and adhesive strength of the obtained aqueous emulsion were measured according to Example 1. However, in the measurement of adhesive strength, diphenylmethane diisocyanate prepolymer (Coronate 3053, manufactured by Nippon Polyurethane Co., Ltd.) was used as a curing agent instead of polyisocyanate. Table 2 summarizes the results.

[0038]

[Table 2]

[0039]

According to the present invention, an aqueous emulsion containing AA-PVA is used to prepare (A) an oxycarboxylic acid and
(B) By containing one or more selected from sulfites, bisulfites, metabisulfites, and thiosulfates, the viscosity of the emulsion is further stabilized while having a sufficient adhesive force. Since the increase in viscosity over time can be reduced, the emulsion can be stored for a long period of time without limiting the intended use, which is extremely advantageous industrially.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI C08K 5:09) (58) Investigated field (Int.Cl. ⁷ , DB name) C08L 29/04 C09J 129/04 C08K 3 / 30 C08K 5/09-5/098

Claims (2)

(57) [Claims] 1. An emulsion comprising acetoacetylated polyvinyl alcohol, wherein (A) oxycarboxylic acid and
(B) A method for stabilizing an aqueous emulsion, comprising one or more selected from sulfites, bisulfites, metabisulfites, and thiosulfates. 2. The method for producing an emulsion containing acetoacetylated polyvinyl alcohol by post-adding acetoacetylated polyvinyl alcohol to the emulsion, wherein (A) and (B) are added before the post-addition of acetoacetylated polyvinyl alcohol. 2. A method for stabilizing an aqueous emulsion according to claim 1, wherein the emulsion is previously blended with either or both of the acetylated polyvinyl alcohol and the emulsion.